Overmatching rotor to stator retarder arrangement to combat cavitation



E. H. LAUER 3,476,219 VERMATCHING ROTOR TO STATOR RETARDE-R ARRANGEMENTNov. 4, 1969 OMBAT CAVITATION d March 22, 1968 Y+ AV INVENTOR. EPA S7 HAAA/2 United States Patent M 3,476,219 OVERMATCHING ROTOR TO STAT ORRETARDER ARRANGEMENT T0 COMBAT CAVITATION Ernst H. Lauer, Richland,Mich., assignor to Eaton Yale & Towne Inc., Cleveland, Ohio, acorporation of Ohio Filed Mar. 22, 1968, Ser. No. 715,362 Int. Cl. F16d57/02, 33/20 US. Cl. 188-90 4 Claims ABSTRACT OF THE DISCLOSURE Field ofthe invention This invention relates to a hydro-kinetic retardermechanism and, more particularly, relates to a construction within theretarder mechanism for minimizing cavitation in the flow of liquidtherein.

Description of the prior art Cavitation has long been recognized as aproblem in fluid circuits of one kind or another and is often a frequentcause of serious structural damage to pumps, propellers and other typesof equipment which affect a fluid or are affected by a fluid. One suchcavitation problem has existed in hydro-kinetic retarder mechanisms forautomotive and similar uses.

Cavitation in the larger ones of the known hydrokinetic retardermechanisms, such as those of 15-20 inches in diameter, has been only aminor problem in view of the relatively low fluid velocities utilizedtherein and consequent small likelihood of any cavitation at alloccurring therein. In a continuing effort to minimize the size ofvarious components which are being introduced into vehicles of one kindor another, attempts have been made to reduce the size of the retardermechanism. However, when the size of the retarder mechanism is reduced,such as to 4-6 inches in diameter, the rotor thereof has to be rotatedat a much higher velocity to develop the necessary pressure within thetoroid so that an effective retarding force will still be generated.With an increase in the speed of rotation of the rotor, the fluid withinthe toroid necessarily changes its own velocity at a faster rate so thatnow the cavitation problems become amplified in the smaller units andare serious, sometimes causing such structural damage as to render theretarder worthless.

In the larger retarder mechanisms cavitation is minimized sufficientlyby obtaining a reasonably close match between the inner and outerdiameters of the stator and rotor. That is, the closer the match, theless cavitation will appear. However, this does not as a practicalmatter solve the cavitation problem for smaller units where thevelocities are enough higher that an amount, either in dimensional termsor percentage-wise, of mismatch which would be permissible in a largerunit creates in a smaller unit a degree of cavitation which willseriously damage, or even totally destroy, such unit.

Furthermore, the expense involved in manufacturing matching rotors andstators is high. The time required to find matching sets of rotors andstators, particularly to the accuracy required for small, high speed,units, has been excessive and has further increased the overall ex-3,476,219 Patented Nov. 4 1969 pense of the smaller retarder units. As aresult, the industry has been faced with the problem that in spite oftheir greater desirability from many points of view, the smallerretarder mechanisms could not be produced at a reasonable cost. Thus,the design criteria for hydrokinetic retarder mechanisms of the largervariety are not entirely satisfactory for the design of the smallerhydrokinetic mechanisms and apparatus which will minimize thecriticality of matched rotor and stator combinations will beadvantageous.

Accordingly, the objects of the invention are:

(1) To provide a hydro-kinetic retarder mechanism which eliminatescavitation of a damaging magnitude from the toroidal flow of thehydraulic fluid therein.

(2) To provide a hydro-kinetic retarder mechanism which minimizescavitation in the toroidal flow of the hydraulic fluid therein.

(3) To provide a hydro-kinetic retarder mechanism which minimizescavitation in the toroidal flow of the hydraulic fluid thereinparticularly at the points of transfer from the rotor to the stator andfrom the stator to the rotor.

(4) To provide apparatus, as aforesaid, which is capable of productionwithin standard and easily obtainable tolerances.

(5) To provide apparatus, as aforesaid, which involves less time inassembly and, therefore, results in less overall expense for theproduction of said retarder.

(6) To provide apparatus, as aforesaid, wherein the inner and outerdiameters of the annular concave surface of the rotor and stator canvary within easily attainable tolerances without appreciably affectingthe tendency to cavitation of the retarder mechanism.

(7) To provide apparatus, as aforesaid, wherein the life of thestructural parts is lengthened due to the minimization of cavitationtherein.

Other objects and purposes of this invention will be apparent to personsacquainted with apparatus of this general type upon reading thefollowing specification and inspecting the accompanying drawing.

Brief description of the drawing FIGURE 1 is a central longitudinalsectional view of a retarder mechanism embodying the invention takenalong the line II of FIGURE 3.

FIGURE 2 is an enlarged fragmentary sectional view of a portion of theretarder mechanism illustrated in FIGURE 1.

FIGURE 3 is a partial sectional view taken along the line 'IIIIII inFIGURE 1.

FIGURE 4 is a sectional view taken along the line IVIV in FIGURE 3.

Certain terminology will be used in the following descriptive materialfor convenience in reference. The words front and rear will designatedirections axially to the left and to the right, respectively, of theshaft illustrated in FIGURE 1. The words inwardly and outwardly willrefer to directions toward and away from, respectively, the geometriccenter of the device and designated parts thereof. Said terminology willinclude the words above specifically mentioned, derivatives thereof andwords of similar import.

Summary of the invention In general, the objects and purposes of theinvention are met by providing a turbine retarder mechanism forretarding the rotation of a shaft, said turbine including a rotorrotatable with said shaft and a stator axially spaced therefrom, both ofsaid rotor and stator having internally facing annular concave surfacesin which the inner and outer diameters of one of the concave surfaces ofthe rotor are greater than the corresponding inner and outer diametersof the other of said concave surfaces on the stator. By this, steps aredeliberately formed between all of the adjacent edges of the two facingconcave surfaces, which steps oppose the toroidal flow of fluid. It hasbeen discovered that such predetermined deliberate offsetting does notappreciably increase turbulence but holds the tendency to cavitationwithin commercially acceptable limits.

Detailed description A retarder mechanism .10' is illustrated in FIGURE1 and generally comprises a housing 11 having an opening in the centerthereof through which extends a shaft 12 I- tatably supported bybearings 13 and 14. The housing 11 also has an inlet chamber 16 (FIGURE3) which is supplied with fluid through the conduit 17. The housing 11also has an outlet chamber 18 and a conduit 19 which removes the fluidtherefrom. A plurality of threaded openings 24 are located on the frontface of the housing 11.

In this particular embodiment, the stator 21 is secured to the housing11 by any convenient means, such as the means discussed below, has anannular concave surface 22 on the front face thereof and has a pluralityof of passageways 23 (FIGURES 3 and 4) formed therein which arecommunicable with the inlet chamber 16. The passageways 23 flare bothradially and circumferentially at each of their ends in order to obtainthe most efficient fluid flow into the turbine structure in accordancewith well-known and accepted turbine-design techniques. This type ofconstruction is illustrated in more detail in Patent No. 3,335,- 823,issued Aug. 15, 1967.

A rotor flange 26 is secured by a nut 27 to the front end of the shaft12 and extends radially outwardly therefrom and is axially spaced fromthe front surface of the stator 21 a distance which will obtain the mosteflicient fluid flow in the turbine structure and which is well knownand acecpted in turbine-design techniques. An annular concave surface 28is located on the rear surface of the rotor 26 opposite the forwardlyfacing annular concave surface 21 on the stator 13. The concave surface28 is provided with partitions 29 (FIGURE 4) which are, in thisembodiment, arranged angularly at about 45 degrees with respect to thegeneral plane of the concave surface 28 and are related to the directionof rotation of the rotor 26 as indicated by the arrow in FIGURE 4. Thistype of construction is also illustrated in the aforesaid Patent No.3,335,823.

A cap 31 is placed over the rotor and stator assembly to prevent anescape of fluid from the fluid system. The cap 31 includes an annularring 32 which both supports a cupshaped shell 36 and surrounds thestator 21 to clamp same to the housing 11. In this embodiment, said ring32 has a plurality of openings 33 therein which are in alignment withthe threaded openings 24 in the housing 11. A plurality of bolts 34 arereceivable in the openings 33 and 24 and threadedly secure the annularring 32 to the housing 11. The shell 36 is secured to the ring 32 by anyconvenient means such as Welding. The center portion of the shell 36 isprovided with an opening 37 therein through which extends a conduit 38secured thereto as by welding. The conduit may be utilized in a mannersimilar to that shown in Patent No. 3,291,268, filed Aug. 10, 1964.

An annular chamber 39 is formed adjacent the inner diameters of therotor 26 and stator 21. A passageway 41 indicated generally by thedotted line in FIGURE 1, connects the chamber 39 to the outlet chamber18.

The descriptive material discussed hereinabove is considered to beconventional and forms no part of the invention. What is considered tobe novel is that the inner and outer radii X and Y, respectively, of theconcave surface 22 of the stator 21 is made less than the correspondinginner and outer radii "X +AX and "Y+, respectively of the concavesurface 28 of the rotor 26. The differential AY thus created between theouter radii of the stator is critical inasmuch as too large adifferential, that is, too

much overlap, tends to aggravate cavitation rather than minimize it andusually results in damage to the concave surfaces 22 and 28 adjacent theouter edges thereof. It has been found through experimentation thatwhere the discharge'from the torus is at its inner diameter adilferential AY in the range of .000 to +.O15 inch on a three inchradius is optimum. The differential AX thus created between the innerradii of the stator and rotor in the same type of unit is also criticalinasmuch as too large a differential would allow too much fluid to spillover from the torus defined by the concave surfaces 22 and 28 and thusdecrease the energy absorption capacity of the retarder. It has beenfound through experimentation that a differential AX in the range of+.02O to +.O40 inch on a one and half inch radius is optimum. It is tobe noted that the differential AX is somewhat greater than thedifferential AY to provide discharge space at the ID of the torus inaddition to minimizing cavitation.

It has also been observed that the size of the outlet passages 39 and 41affect the dilferential AX in an inverse relationship. That is, thesmaller the outlet, the greater the overlap must be in order to build upthe required pressure within the torus for satisfactory operation of theretarder mechanism.

Where the discharge from the torus is at its OD, then the values abovegiven for AX and AY are reversed.

It will be recognized that the specific dimensional ranges given aboveare only examples of particular embodiments which have been constructedand successfully operated according to the invention. Further, thesedimensional ranges will be found effective for a wide range of sizes andof requirements for manufacturing tolerances. Nevertheless, so long asthe dimensional requirements herein set forth are met, referringparticularly to the holding of X and Y at dimensions less than X +AX andY-l-AY respectively, variations from the specific dimensions givenwithin the operating limits also serve above set forth may be made asneed to meet other design requirements or to fit other requirements ofmanufacturing tolerances.

Operation The operation of the device embodying the invention will bedescribed in detail hereinbelow for a better understanding of theinvention.

The shaft 12 of the retarder 10 is driven for rotation by any suitabledevice which requires a retardation of its speed. Such a device can be,for example, a transmission which forms a part of a vehicle driven by aprime mover or internal combustion engine as illustrated in theaforesaid Patent No. 3,335,823. The retarder unit may be renderedoperative or inoperative at the will of the operator by suitable manualcontrol (not shown) so that fluid is introduced into the retarder unit10 through the conduit 17 into the inlet chamber 16. The air previouslywithin the retarder unit 10 will be carried away by the liquid asdesired, but most conveniently to a reservoir where it will bleed out byany suitable means (not shown) such as that associated with, forexample, the radiator of the vehicle discussed in the aforesaid patent.

Introduction of liquid into the chamber 16 and thence through thepassageways 23 will fill the torus defined by the concave surfaces 22and 28. This will permit the rotor 26 to act against said liquid andimpart energy thereto. The fluid circulates through the torus in aspiral path. It flows from the stator to the rotor at the inner diameterand from the rotor to the stator at the outer diameter as indicated bythe arrows in FIGURE 1.

Since there is a difference in the respective inner and outer radii,that difference being AX, some of the liquid-is thrown out ofcirculation while the rest is forced to flow along the curvature of theconcave surfaces 22 and 28. Since a positive match has been created, itis impossible for voids to form which result in cavitation. Moreparticularly, when liquid flows from the stator 21 toward the rotor 26at the inner radii thereof, part of the liquid passes across the gaptherebetween and part of the liquid flows into the chamber 39, thencethrough passageway 41 to the outlet chamber 18. 'In the other instancewhere the liquid is flowing from the curved surface 28 of the rotor tothe curved surface 22 of the stator at the outer radii thereof, part ofthe liquid continues circulating through the stator and a very smallpart of the liquid is expelled into the chamber defined by the shell 36of the cap 31.

As the retarder increases in speed, a pressure builds up in the chamberdefined by the cap 31 and a high torque is built up in the retarder.Therefore, by connecting the conduit 38 to a control (not shown) in amanner similar to that shown in the aforesaid Patent No. 3,291,268, thetorque is reduced at high speeds while maintaining useful torque at lowspeeds.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be understoodthat variations or modifications of the disclosed apparatus, includingthe rearrangements of parts lie within the scope of the presentinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a turbine retarder, the combination comprising:

a rotatable shaft;

a turbine for retarding the rotation of said shaft and including abladed rotor rotatable with said shaft and a stationary bladed statoraxially spaced therefrom, said rotor and said stator having internallyfacing annular concave surfaces defining a torus;

fluid input means positioned intermediate the inner and outer radialextremities of said rotor and stator for supplying a working fluid tosaid torus during operation, said blades on said rotatable rotor andsaid stationary stator initiating a toroidal flow of said working fluidin said torus;

fluid outlet means positioned at one of the inner and outer radii ofsaid torus for permitting an egress of a portion of said working fluidfrom said torus during operation;

both the inner and outer radii of the concave surface on said rotorbeing greater than both the corresponding inner and outer radii of theconcave surface on said stator to define steps between the adjacentedges of said annular concave surfaces which oppose the toroidal flow ofsaid working fluid in said torus whereby cavitation occurring betweenthe torus halves upon toroidal flow of fluid therebetween is at leastsubstantially eliminated, the difference between said radii at said oneof said inner and outer radii being greater than the difference betweenthe radii of the other of said inner and outer radii to provide adequateclearance for the egress of said portion of said working fluidtherethrough, further fluid outlet means positioned at said other ofsaid inner and outer radii for permitting an egress of the remainingportion of said working fluid from said torus.

2. The turbine retarder defined in claim 1, wherein said portion of theworking fluid is discharged at the inner diameter of the torus and thedifferential between corresponding outer radii is in the range of .000to +.015 inch.

3. The turbine retarder defined in claim 1, wherein said portion of theworking fluid is discharged at the inner diameter of the torus and thedifferential between corresponding inner radii is in the range of +.020to +040 inch.

4. The turbine retarder defined in claim 1, wherein the differentialbetween corresponding radii for the portion adjacent the discharge ofthe torus is +0020 to +0.040 inch and the differential of the othercorresponding radii is -0.000 to +0.015 inch.

References Cited UNITED STATES PATENTS 2,425,171 8/1947 Bennett et al.188-90 2,660,970 12/1953 Koskinen 103-115 X 2,696,081 12/1954 Kiep -542,748,570 6/ 1956 Booth. 3,291,268 12/1966 Nagel 188-90 X FOREIGNPATENTS 921,570 3/1963 Great Britain.

GEORGE E. A. HALVOSA, Primary Examiner US. Cl. X.R. 60-54; 103-96 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,2l9 DatedNovember 4 1969 Inventor(s) Ernst H. Lauer It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 3 line 72 "and "Y respectively" should read and, "Y +AY",respectively Column 4 line 15 one and half" should read one and a halfline 37 cancel "serve".

Signed and sealed this 25th day of August 1970 (SEAL) Attest:

EDWARD M,PLETC IHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

